The present application is claims priority of Chinese patent application Serial No. 200610127652.7, filed Sep. 5, 2006, the content of which is hereby incorporated by reference in its entirety.
Since 9/11 in U.S., security-inspection of aviation is becoming more and more emphasized. Besides traditional security-inspection of packs, security-inspection of the liquid articles carried by passengers is added. Accordingly, means and methods of a quick security-inspection of the liquid articles in packs are in dire need.
Nowadays, there are four types of detection methods used in security-inspection of liquid articles, including the chemical method, the electromagnetic method, the neutron detection method and the radiation detection, method, as follows:
1) The chemical method can be subdivided into the odor identification method, the ion scanning explosive detection method and the substance analysis. The odor identification in practical applications often fails to implement detection because of sealed and packaged conditions of liquid articles. The ion scanning explosive detection method is known for its high sensitivity, but with high false alarm rate, it suffers from the effects of background environment. The substance analysis is of high precision and high accuracy, but this method needs a certain period of time to analyze the sample, which cannot meet the demands of on-site quick detection.
2) The electromagnetic method works in an active measurement manner. It distinguishes liquid articles from each other according to their dielectric constants in the electromagnetic field. The electromagnetic method is easily subjected to severe effects of metal packages or other thick material packages. As a result, the electromagnetic method is limited in the case of complex package materials.
3) The use of the neutron, detection method will leave residual radiation remaining in the detected liquid due to the effect of “neutron activation”. Furthermore, the radiation shielding is complicate true to neutrons' strong perforation, and the apparatus has to take a large area, so the method is not suitable for application in the security-inspection systems of civil aviation.
4) Currently, most of the security-inspection apparatuses of civil aviation are radiation apparatuses. In these apparatuses, the X-ray. 2D imaging technology and the three-dimensional CT technology are mostly adopted. These technologies, which are mainly used for security-inspection of packs, fail to accomplish the security-inspection of liquid articles in packs.
The X-ray 2D imaging technology acquires two-dimensional projection images by integrating three-dimensional information of articles to be detected along X-ray's direction. These images show difference in the form of grayscale or pseudo-color, to give the operator a vivid display. However, the X-ray 2D imaging technology is in defect of one-dimensional information of objects, so the detection of liquid articles is suffering from severe affection of shapes and sizes of the liquid articles.
The three-dimensional CT technology is the extension and application of CT technology. The CT technology was applied in the diagnostics first, which was implemented by conducting a multi-angle projection of respective slices of an article. By using a computer to reconstruct the multi-angle projection data of respective slices, reconstructed images were obtained. The information of the different attenuation coefficients in the reconstructed images was displayed in the form of different grayscales, by which the inner differences of the articles were displayed. With the development of the CT technology, the industrial CT for the nondestructive inspection and the package CT for the security-inspection were put into use, with the goal remaining to be acquiring the slice images of the inner difference of articles. Therefore, with the traditional X-ray 3D imaging technology for thee liquid articles, only the slice images with no differences can be seen,
Thus, it is difficult for the security-inspection devices of the CT type to gain popularity, for their high cost and bulkiness, as a result of the wide range of the articles that can be detected by them.
To sum up, for the quick detection of the liquid articles the chemical method, the electromagnetic method and the neutron detection method are not suitable for quick security-inspection. By using the X-ray 2D imaging technology and the three-dimensional CT technology, grayscale images or pseudo color images with contrast are acquired, but these images cannot work as sufficient evidence fear the security inspection of the liquid articles.